1. Field of the Invention
The present invention generally relates to information recording techniques and, more particularly, to an optical information recording technique for recording information on an optical information recording medium having a multi-layer recording layer that contains an information recording area.
2. Description of the Related Art
In recent years, with improvement in their functions, personal computers (hereinafter, may be abbreviated as PCs) have become capable of handling audio-visual (AV) information such as music information or image information. Since an amount of the AV information is extremely large, optical discs such as CD (Compact Disc) or DVD (Digital Versatile Disc) have attracted attention as an optical information recording medium. Then, a price-reduction of the optical discs such as CD or DVD has progressed, which results in that an optical disc drive unit as an optical information recording apparatus has become popular as one of peripheral devices of personal computers.
As a recording/reproducing method applicable to such an optical disc, there are known a constant linear velocity (CLV) method, a constant angular velocity (CAV) method and a zone CLV (ZCLV) method that combines the CLV method and the CAV method. According to the CLV method, an optical disc is rotated at a constant linear velocity, which gives little complexity to data management or rotation speed control since a rotation speed is constant and a linear velocity is increased as it goes to an outer side, but is capable of providing a large recording capacity. On the other hand, according to the CLV method, it is necessary to increase a rotation speed of an optical disc as a recording point goes inner side of the optical disc, which makes it difficult to rotate the optical disc at such a high speed. Moreover, an increase in the rotation speed of the optical disc may cause a problem of increasing motor cost, increasing sound and vibration or difficulty in servo system design.
In this regard, the CAV method rotates an optical disc at a constant angular velocity (rotation speed), which makes easy to manage data or control the rotation speed. However, a recording capacity achieved by the CAV method is smaller than that of the CLV method. Additionally, according to the ZCLV method, an optical disc is divided into a plurality of zones in a radial direction so that a linear velocity is constant within each zone. Then, a rotation speed is varied so that the linear velocity is increased as it goes to outer side of the optical disc. Therefore, the ZCLV method has the advantages of both the CLV method and the CAV method.
However, even if a recoding is performed according to the ZCLV method, when attempting a higher recording speed, there is a limitation in an output power of a semiconductor laser as a light source used in an optical disc drive unit. For this reason, for example, there may be a case in which a recording power necessary for achieving a desired recording characteristic exceeds a maximum output power of a semiconductor laser when an insensitive optical disc is used.
Thus, usually, an optical disk drive unit performs a test write on an optical disc to record before starting recording on the optical disc. Then, the optical disk drive unit acquires an optimum recording power based on a reproduction signal characteristic obtained by reproducing information recording in an area where the test write was performed so as to perform the recording with the thus-obtained optimum recording power. Thereby, a good recording quality can be achieved. Hereinafter, the acquisition of the optimum recording power based on the reproduction signal obtained from the area where the test write is performed is referred to as an optimum power control (OPC). The area where the test write is performed when performing the OPC may be referred to as a power calibration area (PCA).
In recent years, a multi-layer optical disc having a recording layer containing a plurality of layers instead of single layer has been developed. As such a multilayer optical disc, there is known one which uses an organic dye material in addition to a reproduction only optical disc having multilayered embossed pits. Since the organic dye material reacts with light irradiation and has transparency (high optical transmittance), the organic dye material is suitable for a material of the multilayer optical disc.
Japanese Laid-Open Patent Application No. 2003-22532 discloses an optical disc apparatus for performing recording or reproduction on such as multilayer optical disc.
In the meantime, there is a problem mentioned below when performing a recording on a multilayer optical disc having a recording layer containing a plurality of layers. For example, when recording information on a second recording layer of a two-layer disc having two recording layers on the same recording side, the recording of the second recording layer is performed by transmitting a light beam through the first recording layer. Therefore, an amount of the light beam reaching the second recording layer may be changed depending on a state of the first recording layer as to whether it is in an erased state (high reflectance, low transmittance) or a recorded state (low reflectance, high transmittance). Accordingly, there is a problem in that an optimum recording power acquired by OPC is changed due to changes in the amount of the light beam. Such a fluctuation in the optimum recording power may be a cause of degradation of recording characteristic such as a jitter or an error rate of the second recording layer.